The field of the invention is fluid catalytic cracking (FCC).
FCC technology, now more than 50 years old, has undergone continuous improvement and remains the predominant source of gasoline production in many refineries. This gasoline, as well as lighter products, is formed as the result of cracking heavier, less valuable hydrocarbon feed stocks such as gas oil.
In its most general form, the FCC process comprises a reactor that is closely coupled with a regenerator, followed by downstream hydrocarbon product separation. Hydrocarbon feed contacts catalyst in the reactor to crack the hydrocarbons down to smaller molecular weight products. During this process, coke tends to accumulate on the catalyst which is burned off in the regenerator.
Naphtha is most plenteously produced in an FCC unit and is made into gasoline when lighter hydrocarbons are removed. LPG is a lighter hydrocarbon produced in an FCC unit which may contain valuable light olefins that can be recovered. Light cycle oil (LCO) is a heavier hydrocarbon stream produced in an FCC unit that can be directed to the diesel pool. Heavy cycle oil (HCO) is an even heavier FCC liquid stream pumped around to cool the main fractionation column but is typically not recovered as product. Slurry oil is the heaviest FCC product that is typically burned as fuel after catalyst is removed from it.
The demand for diesel has increased over gasoline in recent years. Increased recovery of LCO produced in an FCC unit can be directed to the diesel pool and augment diesel production.
Demand for propylene continues to outstrip supply. Further recovery of light olefins would also be desirable.